The present invention concerns an angle-of-rotation sensor with a stationary component and a rotating component. The stationary component includes a stator accommodated in a housing with at least one base. The stator is in two halves of ferritic material separated by space. The rotating component includes an annular magnet accommodated in a holder and rotating around the stator with an airgap left between them.
An angle-of-rotation sensor of this genus is known from the WIPO Patent Publication No. WO A 95/14911, which is assigned to the present applicant. It comprises a stationary component and a rotating component that moves in relation to it. The stationary component has two mutually facing stator halves with space between them.
The rotating component includes an annular magnet accommodated in a holder.
There are drawbacks to this embodiment. The connections to other parts of the device or the vehicle engine are difficult to perform, because the poles of the magnet are difficult to position properly with respect to the space between the stator halves while the sensor is being assembled.
The principal object of the present invention is accordingly to provide a more accurate angle-of-rotation sensor of the aforesaid genus that will be easer to manufacture and assemble. The stationary component in particular will be simpler, the magnet holder as magnetically insulating as possible. The assembly and connection of the sensor should be easily made. This object is attained as recited in the body of Claim 1.
This object, as well as other objects which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, in an angle of rotation sensor of the type described above, by the following features:
(a) the ferritic stator halves are stator halves, with at least one holder secured in or on a baseplate of non-magnetic material;
(b) the magnet is positioned in the holder by at least one cut-out gap and at least one matching web at a specified angle xcex1 to the space; and
(c) the baseplate is connected to at least one conductor that connects at least one component and at least one coupler.
Stators are easy to sinter, precise and stable. The complicated stacking procedure is eliminated. One particular advantage is that each sintered stator half can be fastened to the baseplate extremely accurately. The magnet holder can be cost effectively and, in particular, precisely fabricated by metal-injection molding (MIM). Complicated additional shaping, especially machining, of the material is unnecessary. The holder will hold the magnet exactly where it should be within precises tolerances. Measurements will be considerably more precise. The web or space will simultaneously position the magnet precisely in relation to the space during assembly. No complicated readjustments will be necessary. It will accordingly be possible to position the magnet""s pole at a right angle, perpendicular that is, to the space between the two facing stator halves. If any angle other than a right angle is needed in special cases, it can be established ahead of time for all the angle-of-rotation sensors in the same series. Most significant, however, is that the magnet will be secured too tight to turn. Two alternative embodiments of the stator holders are possible. They can be either sintered bolts or sintered feet. Whether bolts or feet, they can terminate in a sintered cap. This feature ensures that the sintered stator half is secured, stationary, in the baseplate. The baseplate can be a stator baseplate with at least one stabilising cutout.
The stator baseplate can comprise the base of the stationary component housing and have stabilising cutouts with sintered stator halves fitting into it along with their feet and caps.
The stator baseplate can be plastic or other non-magnetic and non-conductive materials.
The halves can be sintered to final dimension, finally positioned, and forced into the base of the housing as a whole. The essential advantage of this approach is the extremely cost-effective stabilisation and fastening of the halves. The stationary component can accordingly be finally fabricated in only two basic steps.
The housing and its base can be of plastic, preferably injection-molded to ensure that the stationary component constitutes a precisely dimensioned component of the sensor.
Two alternative embodiments of the metal-injection molded holder are possible.
It can be a cup metal-injection molded in one piece of magnetic material with an essentially round foot, at least two, preferably cylindrical stems rising out of one edge of the foot, and an essentially round and hollow bowl resting on the stems. A one-piece bowl is considerably less expensive to manufacture. Such a cup can be molded of magnetic material in a single mold. The molding will be 30 percent oversize and will need to be heated and sintered to its final dimensions.
To allow at least extensive magnetic insulation of the cup from the components to be mounted on it, the stems can magnetically insulate the foot from the bowl.
The holder can alternatively be metal-injection molded in two parts, comprising an essentially straight-sided bowl with a round base of metal-injection molded of a non-magnetic material, provided in a second molding stage with a cylindrical wall of magnetic material. The resulting bimaterial molding will be 30 percent oversize and will need to be more or less sintered to its final dimensions. The base and wall will accordingly be precisely dimensioned and will fit together perfectly tightly. The wall will be precisely positioned. The non-magnetic material of the base will ensure effective magnetic insulation from any components to be mounted on the bowl. One particular advantage is that the base of the bowl can be provided with a cutout that will readily accommodate a simply inserted valve shaft. This feature will compensate for the extra expense of two-part manufacture.
A gap can be cut out of the bowl in either embodiment. If the magnetic wall is provided with at least one matching web, the poles of the wall can be positioned at a right angle, perpendicular that is, to the space between the mutually facing stator halves. If, in a special case, the angle is to be other than a right angle, it can be a cup-like body established for all the products in a single series.
The Hall sensor or sensors and the plug unit can be connected by a stamped lead frame. The lead frame can be held within the housing unit.